Chemicals (blood markers and tracers) containing a radioisotope (hereinafter referred to as an RI) have a property of being selectively taken into specific tissues or organs in a living body. A nuclear medicine diagnostic apparatus uses this property to detect a gamma ray emitted from an RI distributed in a living body with a gamma ray detector provided outside the living body.
A detection result of the gamma rays is used for generation of a nuclear medicine image that has a brightness distribution corresponding to a dose distribution of the gamma rays. Brightness values of the nuclear medicine image reflect a concentration distribution of an RI in an object. Accordingly, a user can use the nuclear medicine image for such purposes to diagnose functions of organs and the like in the living body.
In one method for generating a nuclear medicine image, incident photons are counted per display pixel based on positional information included in a detection result of gamma rays, and pixel values (hue, saturation and brightness) of each display pixel are determined by using a color look-up table (hereinafter referred to as a LUT) that associates count numbers and pixel values (color) so as to generate an image.
However, if a predetermined LUT is used for a nuclear medicine image taken by whole body photographing, regions with a tendency for high RI concentration have a high brightness, while regions with a tendency for low RI concentration, such as a liver, become poor in contrast.